cmpthese -1,{
    a=>q[ my( $a, $b    ) = ( 1, 2 ); ( $a, $b ) = ( $b, $a )   for 1..1000; ],
    b=>q[ my( $a, $b,$t ) = ( 1, 2 ); $t = $a, $a = $b, $b = $t for 1..1000; ],
    c=>q[ my( $a, $b    ) = ( 1, 2 ); $a ^= $b ^= $a ^= $b      for 1..1000; ]
};;
    Rate    a    b    c
a 3253/s   -- -34% -42%
b 4913/s  51%   -- -13%
c 5632/s  73%  15%   --